DIAZQ4NITIATE Preparation, Properties, and Evaluation J. 31. WILLIS, GLEN ALLIGER, B. L. JOHNSON, AND W.RI. OTTO Chemical and Physical Research Laboratory, The Firestone Tire and Rubber Co., Akron, Ohio
T
HROUGHOUT the great majority of the many investigations on rubberlike synthetic polymers, the initiators employed have been peroxides, either water-soluble (potassium persulfate being the chief example) or oil-soluble, such as benzoyl peroxide or diisopropylbenzene monohydroperoxide. The most notable departure from these initiators has been the use (10) of the diazothio ethers, 4-methoxybenzenediazomercapto2-naphthalene (MDK) and 4-methylbenzenediazomercapto-2naphthalene (TDN). These materials have proved to be suitable initiators and also to have some activity as modifiers. However, their possibilities have been explored principally a t a polymerization temperature of 41" F. Thus, the field of initiators has been subject to less widespread investigation than most of the other variables in a typical synthetic rubber recipe. The purpose of the present investigation was to develop different initiators, if possible, of a type which would lead to improvement in polymer structure at 122" F. It was felt from the outset that diazo-type compounds offered the best possibilities for development along these lines. During a preliminary survey of these materials, the object was to find examples which did not have the two disadvantages of the diazothio ethers-high cost and low stability. The use of diazo-type compounds as polymerization initiators has been known for many years. The work of Bysow on the polymerization of butadiene with diazoaminobenzene is an example of this ( 2 ) . A number of patents have been issued relating t o the use of diazo compounds in general as polymerization initiators or activators (1, 3, 4, 6, 8, 11, 18, 14, 16). These patents, hoviever, were directed toward improving the rate of polymerization and did not indicate any outstanding improvement in polymer properties. After detailed study of the properties and reactions of diazo materials in general (9, I S ) , stabilized salts of diazotized aromatic amines were selected as the specific type of compound with the greatest chance of success. The program was begun with the laboratory preparation and evaluation of diazo salts. POLYMERIZATION WITH LABORATORY-PREPARED IXITIATORS AT 122' F.
Stable sodium diaaotate salts were prepared from both aniline and p-nitroaniline by the method of Hickinbottom (6). Polymerization studies were made a t 122" F. with these materials using a 100-gram monomer charge of 70/30 butadiene-styrene in beverage bottles. Other ingredients were: 200 grams of water, 6 grams of soap flakes, and sodium hydroxide, the amount of which was varied, as was the diazo initiator. Some of the later runs were modified with mixed tertiary mercaptans (RITM 4, Phillips Petroleum (30.). The results obtained in this series of runs are presented in Table I. There was a rate increase with increased initiator loading and the p-nitroaniline derivative gave faster reaction than the aniline derivative. It is of interest t o note the ability of this system t o initiate polymerization in the absence of mercaptan, which is not practical in the GR-S system using potassium persulfate. It is possible that the reaction proceeds by the hydrolysis of the diazo salt in aqueous solution to give the oil-soluble diazonium hydroxide, which then diffuses into the oil layer and decomposes t o form free radicals. These aryl free radicals then initiate the polymerization.
The latex from a number of these runs was coagulated with salt-sulfuric acid solution and the polymer obtained was found to be of a characteristic deep red color, particularly in runs where dinitrochlorobenzene was used as the stopping agent. The product from later pilot plant batches in which sodium dimethyldithiocarbamate was used as the stopping agent was light brown in color when dry. The color is probably the result of unreacted diazonium intermediate coupling with other portions of the reaction system which may or may not be part of the polymer chain.
TABLE I.
308 275 292 315 314 a
122" F.
DIAZOS.4LTS
Time, ConrerMTM 4 , Hours d o n , % %/Hour Part p-Nitroaniline Deiivative 0.1 0.025 16.25 84 5.2 0 0.2 0.025 17 95 5.6 0 0.2 0.3 18.5 82 4.4 0.35 0.2 0.3 18.: 87 4.7 0 0.5 0,025 57 10.3 0 0.5 0.025 72.5 10.3 0 Aniline Derivative 0.15 0.025 23 61 2.7 0.3 0.2 0.025 16 GO 3.7 0 0.2 0.025 16 71 4.4 0 0.2 0.3 18.5 87 4.7 0 0.2 0.3 26 55 2.1 0.35 Portion insoluble in toluene after 48 hours, unstirred.
R u n Diazo, No. Part 272 271 316 317 274 306
P O L Y J I E R I Z A T I O N WITH LBBORBTORY
NaOH, Part
AT
yo
Gel0 91.8 91.8
... ...
86.3 ,.
0.G 67.7 52.6
. . ,.
,
Polymer from run 308 (Table I) was compounded in a standard tread stock as follows: Po1y m er EPC black Sulfur Zinc oxide Stearic acid PBNA Softener Santocure
100 45 1.7 2.4 2.5 0.6 6.6 1.2
Physical tests on this stock compared to GR-Sin the same recipe are presented in Table 11. The results showed sufficient improvement over GR-S to warrant a much more detailed study of this type of initiation. Higher tensile strength and rebound and lower operating temperature were particularly noteworthy. POLYMERIZATION WITH NITRAZQLE CF AT 1 2 2 O F .
I n selecting a commercial diazo salt for use in runs on a larger scale, approximately 20 different examples were evaluated. They varied considerably in the number and type of substituents on their aromatic rings. Initiator activity varied from zero up t o a maximum reached by the following three samples: Nitrazole CF, General Dyestuff Corp. Fast Red GG salt, The Hilton-Davis Chemical Co. Fast Violet B salt, Otto B. May, Inc. The first two materials are stabilized salts of diazotized pnitroaniline and the third of 6-benzoylamino-4-methoxy-mtoluidine. The material arbitrarily selected for the remainder of the study was Nitrazole CF because it was on hand in substantial quantity.
1316
INDUSTRIAL AND ENGINEERING CHEMISTRY
June 1953
1317
loadings are compared show a noticeable increase in reaction PROPERTIES OF DIAZO-INITIATED time for the former. This indicates that the oxygen does play a TABLE 11. PHYSICAL POLYMERS part in the Nitrazole recipe. (70/30-BD/ST, standard tread stock) GR-S X546a 37 35s 41E K2S208 CHPd Nitrazole C F AIBNe
Polymer Initiator
308 Diaz.
__
I
p-NA
Polym. temp., F. Wms. plasticity, mm. Compd. Wms. plast. Cure, Min. a t 280" F. 40 60 80 120 40 60 80 120 40 60 80 120
r
72'F 212O F:: Cold 3-lb. penetration Hot '3-lb. penetration Deflkction, % Running temp., F. Blowout time, min. Dynamic mod., lb./ sq. inch Static mod., lb./sq. inch Int. friction, lb./sq. inch Normal Aged 4 days a t 212O F.
122 3.41 8.21
41
122 122 122 122 , 3 . 5 5 4.06 4.10 3.50 3.57 3.78 4.25 .. 400% Modulus, Lb./Sq. Inch 525 900 950 1050 900 300 1450 1575 1525 1650 950 1475 1975 1725 1850 2025 1675 1300 2325 1950 2000 2200 1675 1775 Tensile, Lb./Ss. Inch 1950 3450 3450 3675 2750 1575 3650 3675 3900 3750 3450 3425 3800 3675 3725 3600 3225 3800 3750 3550 3475 3375 3300 3950 Elongation, % 840 760 760 750 1100 760 660 570 640 620 660 810 570 550 600 580 730 600 530 500 530 540 670 580 Rebound, % (80-Min. Cure) 45 49 46.5 48.5 49 47.5 63 62.5 61.5 63 58.5 56.5 Flexometer Tests 48 49 47 52 50 62 70 67 78 74 1 9 . 3 20.0 ... 1817 21.3 21.3 260 232 245 240 266 270 .. 32 30 31 15.5 17.5 Forced Vibrator a t 100' C. (80-Min. Cure)
.. .. .
177
182
175
180
170
115
122
150
140
140
I
5.0 5.1 4.5 4.2 4.8 Cut Growth, Inches/Hour (80-Min. Cure) 0.8 0.2 1.1 0.5 0.3 4 6
a
Cold rubber.
C
DresinnG~214run. Cumene hydroperoxide. a.u-Arodiiaobut),ronitrile.
4.3
10.5
4.3
3.0
.
.. ..
..
12.0
b 09-free . _ svstem. ~~~~
d 8
+
*
The laboratory evaluation of Nitrazole C F proved that it was suitable in the polymerization recipe given above with only small changes. It proved desirable to use 0.3 part of sodium hydroxide in the recipe and, a t this level, either 0.05 or 0.1 part of the Nitrazole was effective. The emulsifier level (soap flakes) was successfully reduced to 4 parts when the sodium hydroxide and Nitrazole were held a t the 0.3 and 0 . 1 level, respectively. A more detailed study of polymerization rate as a function of Nitrazole C F loading, using 0.3 part of sodium hydroxide and 4 parts of soap flakes, indicated ah increase in rate up to 0.1 part, above which the rate remained constant. When Dresinate 731 or 214 (Hercules Powder Co.) was substituted for soap flakes, a somewhat reduced polymerization rate was obtained, particularly with the latter. A higher caustic loading was somewhat more effective. Details of these runs are recorded in Table
111. Stopping agent studies indicated that 0.2 part of di-lertbutylhydroquinone (Santovar 0, Monsanto Chemical Co.), 0.3 part of dinitrochlorobenzene (DNCB), or 0.1 part of sodium dimethyldithiocarbamate (ADAM) and 0.05 part of sulfur were effective in preventing increase in gel content or Mooney plasticity after their addition to the latex. A study was made of the effect upon polymerization rate of essentially complete removal of oxygen from the system. The technique used for loading an oxygen-free charge included boiling the distilled water used while saturating it with lamp grade nitrogen, blowing all solutions with this nitrogen, and finally purging the bottle with nitrogen before adding the butadiene. Results of polymerizations in which oxygen-free and standard
I n an interesting comparison with the above data, a number of runs were made using a,a'-azodiisobutyronitrile (AIBN, Rohm & Haas Go.) as the initiator. This material is oil-soluble, as compared t o the water solubility of Nitrazole CF. I n this case, the exclusion of oxygen from the system gave a small activating effect. Physical tests on several of these polymers compounded in the standard tread stock (EPC black) are shown in Table 11. I n tensile strength, the diazo polymers are similar to X546 (cold rubber) which gives values 400 to 500 pounds per square inch higher than OR-S. The rebound, running temperature, blowout time, and internal friction are all excellent for the diazo polymers and are superior t o both X546 (LTP) and GR-S. I n aged cut growth resistance, the diazo polymer 37 is inferior, but this appears t o be brought t o the level of the controls by either an oxygen-free system or the use of Dresinate emulsifier. No difference is noted between the use of Nitrazole C F and AIBN as far as physical properties are concerned. Several other variables which may affect physical properties were also examined, but complete test results are not given here. The amount of Nitrazole C F in the polymerization recipe had no effect in the range 0.02 to 0.2 part. An increase in the Mooney plasticity of the polymer resulted in higher tensile strength and better hysteresis properties. Optimum properties occurred a t 60% conversion; higher values gave poor hysteresis and cut growth resistance.
EVALUATION OF NITRAZOLE CF TABLE 111. LABORATORY CATALYST AT 122' F. Nitrazole CF, Part 0.01 0.02 0.05 0.10 0.20 0.10 0.05 0.10 0.20 0.20
Caustic NaOH, Part 0.3
0.50 0.20
0.025 0.3
673 674
0.1 0.1
0.3 0.5
671 672
0.1 0.1
0.3 0.5
Run No. 197-1 197-2 197-3 197-4 197-5 323-2 323-1 321-6 318 319 312 311 321-5
0.50
0.3
0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.2
Emsulifier Soap Flakes, Parts 4 4
4 4 4
Hours Time,
sion, Converyo
16
I f. i .
7 10.75 19.67 19.67
77.5 77.0
19.67 19.67
46.5 60.0
7
0.1
3 Dresinate 731 4 4 KOH Dresinate 214 4 4
7
33
69 79 75 62.5 63.5 67.5 76 65 22 12 34
16 16 16 12.25 15.75 10.75 16 16
LABORATORY INVESTIGATION O F 41O F. DIAZO POLYMERIZATION
As the initial step in the 41 O F. program, two copolymers (70/30 butadiene-styrene) were made a t this temperature with Nitrazole C F initiation and potassium ferricyanide (0.2 part) to accelerate the rate of polymerization. Although with this recipe about 70 t o 100 hours were required for 60% conversion, sufficient copolymer to permit evaluation was made. The physical properties of these copolymers cured in standard tread stock vulcanizates are presented in Table IV. The data indicate that both Nitrazole polymers have considerably higher tensile strength than either the GR-S control polymerized at 122 O F. or the GR-S-100 control (X611) polymerized at 41" F. Further laboratory investigation of low temperature polymerization with diazo initiation was carried on in two general directions, evaluation of diazo compounds other than Nitrazole CF, and examination of a number of standard redox activators with Nitrazole CF. No initiatior was found which gave faster rates than Nitrazole CF, and the best activators were iron pyro-
INDUSTRIAL AND ENGINEERING CHEMISTRY
1318
Vol. 45, No. 6
The emulsifier was a potassium fatty acid soap (5.0 parts), and
TABLE IV. PHYSICAL TESTDATAON 41" F. FERRICYANIDE0.20 part of Redsol was used t o "activate" the 0.15 part of ACTIVATED NITRAZOLE C F COPOLYMERS 10 AND 11
Polymer Prep. temp., O F. Raw M L/4/2 12 Cpd. ML/4/212 Cure 60 min. a t 280' F. MAdulus a t 300% Tensile strength Elongation Ring tensile a t 212' F. Rebound, % 72' F. 212' F. Dyn mod a t 100a C lb./sq. inch Znt. h o t . at looo C.','kilopoises 3-lb. penetrom. Cold Hot Deflection, % Oper. temp., O F. Young's mod., a C. a t 10,000 Ib./sq. inch Aged cut growth, 4 days a t 212O F., 0.01 inch/hour
GR-S 122 47 42
10 41 71 61
11 41 49 51
GR-S-100 41
675 3175 720 900
950 4825 650 875
675 4325 740 1025
1425 3750 660
46 55 182 5.3
47 65 214 4.6
47 61 191 5.0
47 61 235 8.1
43 35 37 72 50 60 21.3 15.3 16.7 263 247 253 -45 -41 -42
45 55 20.0 273 - 46
825
843
858
52
69
...
171
phosphate and iron Sequestrene. A maximum conversion rate of 2% per hour was attained. PILOT PLANT POLYMERIZATIONS
LOKGCYCLEAT 122" F. A fairly large number of pilot plant runs have been made using Nitrazole C F initiation, in batches ranging from 5 up to 500 gallons. Preliminary tests were made in 20-gallon autoclaves with the recipe containing 4 parts of soap flakes as emulsifier. Results were similar to those obtained in laboratory bottle runs, although the reaction cycles may have been somewhat shorter. In an effort t o improve cut growth resistance, Dresinate 731 (Hercules Powder Co.) was used in the recipe; this led t o much slower runs and higher K'itrazole C F requirements. The recipe with 4 parts of Dresinate 731 and 0.075 part of Nitrazole C F initially (plus 0.025 part added incrementwise) was run in the 500-gallon autoclaves to obtain experience on a larger scale as well as a batch of polymer sufficient for factory evaluation. Two series of runs were made; the time cycles ranged from 15 to 39 hours to reach 6070 conversion. I n some cases, an increment of K'itrazole C F was required to keep the charges from "dying out." The two batches of polymer obtained, D332-8 and D346-51, were designated as "long cycle" and were used in the tire tests described later in this report. Polymerization data are shown in Table V. SHORTCYCLEAT 122 F. In view of the impractical nature of slow reactions, further study to shorten the time of polymerization was conducted in the 5-gallon reactors. The logical emulsifier appeared to be a blend of Dresinate 731 and soap flakes. With 4.5 parts of total emulsifier, either a 50/50 or 65/35 blend of Dresinate 731-soap flakes was suitable, while a 75/25 blend resulted in slow reactions. Nitrazole C F was utilized a t the 0.12-0.15 level for best results. The recipe with 4.5 parts of a 65/35 blend of Dresinate 731/soap flakes and 0.15 part of Nitraeole CF has been designated as the "short cycle" recipe, since 60% conversion is reached in 10 to 14 hours. In contrast, 4 parts of Dresinate 731 and 0.1 part of Kitrazole CF are used in the long cycle recipe t o give 60% conversion in 23 to 25 hours. On the basis of the 5-gallon trials of more rapid recipes, polymerizations were carried out in 20- and 500-gallon autoclaves t o provide increased amounts of polymer for half-and-half tread tests, and later, factory evaluations. The 65/35 Dresinate 731soap flakes emulsifier system with 0.15 part of Nitrazole C F was used in all these trials (see Table V). 41 " F. PILOT PLANT RUNS. Early pilot plant polymerizations at 41" F. were slow, as at the time these runs were made, the most effective activator known was potassium ferricyanide. O
Nitraeole. Later runs utilized a ferrous pyrophosphate activator and in one case a 19-hour time cycle was obtained. However, other runs were very erratic and considerably more study is needed. Results are given in Table VI. STRUCTURAL STUDY OF NITRAZOLE CF POLYMER
MACROSTRUCTURE. In an effort to explain the improved properties exhibited by the Nitrazole CF-initiated polymer compared t o GR-S made a t the same temperature, a number of structural studies were made. To simplify the interpretation of the results, the first tests were carried out on polybutadiene prepared in the systems under study. Polymer 544, prepared a t 122" F. in the standard recipe with 0.05 part of Nitraeole C F and carried to 59% conversion and a Williams plasticity of 3.66, was fractionated into the 10 fractions shown in Table 1 7 1 1 . Intrinsic viscosity and osmotic molecular weight values were determined on enough of the fractions t o establish the relationship, [ n ] = 4.93 X 10-41M0.70(Figure 1). Comparison of the molecular weight exponent of 0.7 with the value of 0.45 obtained on polybutadiene produced in the GR-S system a t 122" F. indicates that the polymer chain produced in the Nitrazole C F system is more extended in solution and less cross linked. I n this respect the Nitrazole C F polymer appears
TABLE V. PILOT PLANT RUNSox 70/30 BUTADIENE-STYREYE (Nitrazole C F , a t 122' F. in 500-gallon reactor) Time, ConverHours sion, % hIL4 Run N o . Long Cycle Recipe. Water 180, NaOH 0.3, Nitrazole C F 0.1, Dresinate 731 4.0, BD/S 70/30, MTM Variable
Av. 23 23 58 69 20.8 62 57 19.3 60 52 33 58 58 24.7 60 60 34 54 61 19.4 60 70 Av. 25 Short Cycle Recipe. Water 180, PiaOH 0.3, Nitrazole C F 0.15, Dresinate 731 2.9, Soap Flakes 1.6, M T M Variable 60 66 D352 10.25 13.25 59 77 D353 60 57 D354 14.25 10.0 60 41 D357 17.5 60 57 D358 Av. 13 D332 D333 D334 D335 D336 D337 D338
PILOT P L d S T POLYMERIZATIONS O F 7013 '0 BUTADIEKE-STYRENE AT 41" F. IN NITRAZOLE CF
TABLEVI. Run S o .
B1084 B1087 B1093 B1103
B1127 B1131 B1133
Time, Hours
Modifier
Conversion, 70
ML4
KORR Soap with Ferricyanide (Redsol) Activation MTM 80 0.17 58 71 54 0.20 58 65 80 0.23 52 48 89 0.24 54 42 KORR Soap with Ferrous Pyrophosphate Activation Sulfole B-8 59 38 0.21 19 60 58 0.18 26 58 57 0.18 52
Mixed Soap0 with Ferrous Pyrophosphate Activation Sulfole B-8 40 0.18 60 62 B1132 37 0.18 53 48 B1134 a
66/35, Dresinate 731-NaORR.
INDUSTRIAL AND ENGINEERING CHEMISTRY
June 1953
preferable to polybutadiene prepared a t a comparable conversion in a redox system a t -4 F. Such a polymer (7) has a molecular weight exponent of 0.63. The values for the molecular weight exponent of butadiene polymerized in various systems are listed in Table VIII. The lowered exponent obtained upon increase of polymerization time in the Nitrazole system is also of interest because it is consistent with the thought that cross linking would increase as the time of reaction was lengthened. The correlation of increased cross linking with longer polymerization cycle may also be significant in explanation of the greater tread cracking of tires made from long-cycle Nitrazole copolymer.
method under two conditions: (1) in the extended state a t -85' C.; and (2) in the relaxed state a t 25' C. Considerable order (molecular regularity) was found for the 41 F. Nitrazole C F polymer 1ARl1; a lesser amount was found in the 86' F. Nitrazole C F copolymer 1051-4-8, but none was found for the 122' F. Nitrazole C F copolymers B1050-2-3 and D332-8. Only a very slight amount of order was found in the 41 ' F. cold rubber control, X599, and it is doubtful whether there is any
O
sl
TABLEVIII.
Wt., Grams
of Purified %oolymer
2.22 2.44 0.8 1.59 2.95 3.68 2.67 2.82 2.62 1.29 1.59
9.0 9.9 3.2 6.5 11.9 14.9 10.8 11.4 10.6 5.3 6.5
2.
Intrinsic Viscosity 2.77
5.32 4.35 2.67 1.85 1.50 1.06
Osmotic Mol. Wt. x 10-8
Y
v)
780 326 177
O.l!
73
Conversion,
%
63 64.6 65 60 59
Mol. Wt. Exponent 0.45 0.55 0.63
'
'
I , * I i I I ' 10 100 MOLECULAR WEIGHT M,X 10-4
I I I I *
I
IO00
order in the regular GR-S control C361 (122 F.). Comparing l A R l l (41' F.) with X599 (41' F.), it may be concluded t h a t polymerization a t low temperatures is not the only factor that enhances ordering and that the Nitraaole system is a contributing factor. X-ray diagrams (polymer elongated a t -55" C.) from which the above eonclusions were reached are shown in Figure 2. The infrared spectra of a number of Nitrazole copolymers and one LTP copolymer (butadiene-styrene) were obtained with a Beckman IR2 spectrophotometer using films cast on rock salt plates from carbon disulfide solutions. I n general, the spectra of all the Nitraeole polymers were very similar to the spectra of the control polymers if prepared a t the same temperature. Slight differences in 41' F. Nitrazole polymer appear in the bands due to C=C (near 6 microns) and in the CH2 bands (near 7 microns). The amounts of cis- and trans-l,4 configuration and 1,2 addition, as well as the amount of styrene in terms of per cent by weight, are included in Table X. O
0.61 0.70
Data on molecular weight distribution also suggest that an improvement in macrostructure results from copolymerization in the Nitrazole C F system a t 122 ' F. Comparison of the polymers of Table I X indicates that polymerization in the Nitrazole C F system a t 122' F. shifts the distribution toward polymer of higher molecular weight in the case of butadiene-styrene copolymers. A number average molecular weight of 158,000 obtained on the 122' F. Nitraaole whole polymer (short cycle D352-58) also indicates an improvement over GR-S, which has a molecular weight of 110,000. I n addition to the implication that performance of the 122" F. Nitrazole CF copolymer would be better than that of GR-S, the shift in distribution suggests that use of the Nitrazole C F has altered the relative rates ofinitiation and termination. The decrease in branching and cross linking could also be partly responsible for a shift to higher viscosity in the results on molecular weight distribution. The mechanism of initiation by Nitrazole C F is being investigated further. The molecular weight distribution of a copolymer made in the laboratory a t 41" F. in the Nitraaole system (1AR11) indicates that the reduction in polymerization temperature has resulted in a further decrease in the amount of low molecular weight material (Table IX). MICROSTRUCTURE. Four Nitrazole copolymers of butadienestyrene and two controls were studied by the x-ray diffraction
I
Figure 1. Intrinsic Viscosity-Molecular Weight Relationship for Polybutadiene Polymerized at 122' F.
POLYBUTADIENES F. 122 41 -4 122 122
0 NITRAZOLE CF- 59% CONV mi = 4 . 9 3 ~IO-' M 070 0 GR-S- 63% CONV. l3Q 7 2 . 5 ~ IO-' Mo'"
P
MOLECULAR WEIGHTEXPONENTS OF
Polymerization System Persulfate Redox Redox Nitrazole C F 24.5 hours Nitrazole CF: 13 hours
a
".t
1
10L
TABLEVII. FRACTIONATION AND MOLECULAR WEIGHTDATA FOR 122" F.. NITRAZOLE CF POLYBUTADIENE 544 Polymer Fraction Whole 1 2 3 4 5 6 7 8 9 10 Unprecipitated
1319
.
TABLE X. INFRARED ANALYSESOF NITRAZOLE BUTADIENESTYRENE COPOLYMERS Polymer x599 lARll B 1051-54-58 B1050-62-53 GR-S
O
F.
cis-1,4.
70
trans-1 4 % %I
'
1,2, %
Styrene, %
FLEET TESTS OF 122O F. NITRAZOLE CF POLYMER
A summary of fleet test results on tires with tread stocks utilizing 122" F. Nitrazole C F polymer is presented in Table XI. A brief summary of tread stock physical properties, itemTABLE Ix. MOLECULAR WEIGHT DISTRIBUTION O F BUTADIENE-STY-RENE COPOLYMERS ized by test number, is given in Per Cent Polymer in Eaoh [SI Range Acetone Table XII. Polymer Feature of Polymers Extract 0-1 1-2 2-3 3-4 4-5 5-6 Over 6 X630 GR-9 6.0 28.1 21.6 11.1 12.4 16.1 10.7 The initial test on Nitrazole €3851 Nitrazole long cycle, 20 gal. 9.7 16.0 23.4 14.2 8.9 7.1 9.7 11.0 C F polymer was made with E P C D332-38 Long cycle 500 gal. 9.0 20.5 26.2 14.0 9.3 10.0 10.9 D346-61 Long oycle' 3000 lb. lot 9.5 15.7 29.1 13.8 10.1 11.3 10.3 black and with GR-S-AC as a B1050 Nitrazole short cycle 9.4 17.4 28.2 14.5 9.4 8.9 14.0 1.2 D352-68 Nitrazole short cycle, 3000-lb. lot 9.4 17.9 24.6 18.4 11.4 10.4 7.4 control. A wear rating of 105% X679 Factory production 9.4 17.6 23.8 9.4 11.5 14.4 10.9 3.0 of GR-S-AC was obtained. This lARll Lab, 41' F. Nitrazole 14.0 7.1 26.6 20.5 15.3 7.7 8.8 has been the only test compar-
1320
INDUSTRIAL AND ENGINEERING CHEMISTRY SUMMARY OF FLEET TESTRESULTSox KITRAZOLE C F POLYMERS IN TREADS
TABLE XI.
(122' F., normal Mooney polymers, 0 and X = control and experimental halves of tread)
Test No. 1
R.F.C. Project NO. 120CC
2
120DJ
3
b
X B851-2 X B851-3 0 X611
4
b
0 D332-8
Polymer No. 0 GR-S-AC X B669 0 x599
X D332-8 X B1050 5
Vol. 45, No. 6
204A 204B
X611 D346-51
204C
D352-8
6
b
7
b
0 X611 X D352-8
8
b
0 X611 X D352-8
9
b
X611 D346-51 D352-8
Carbon Feature Black 70/30-BD/ST a t 122' F. EPC Nitr. CF, 70/30-BD/ST at 122' F. soap flakes 23-hr. cycle HAF LTP, 70/30-hD/ST a t 41' F. Dresinate 214 Nitr. C F 70/30-BD/ST a t 122O F. Dresinate 731, 23-hr. cycl: I.TP, ?5/25-BD/ST a t 41 F. HAF Dresinate 214 Nitr. CF, 70/30-BD/ST a t 122' F. Dresinate 731 23-hr. cvcle Nitr. C F , 70/3d-BD/ST" a t 122' F. HAF Dresinate 731, 23-hr. cycle Nitr. CF, 70/30-BD/ST a t 122O F. Dresinate 731/NaORR, 14hr. cycle L T P , 75/25-BD/ST a t 41' F. HAF Piitr. CF, 23 hr. at 122O F. Dresinate 731 Nitr. C F 14 hr. a t 122O F. Dresiiate 731/NaORR, 70/30-BD/ST HAF Same as 5
0 X611 X X679
LTP, 75/25-BD/ST at 41" F. Nitr. CF, 14 hr. a t 122O F. Dresinate 731/NaORR, 70/30BD/ST Same as 7 Treads lab pressed for 7 and factory tubed for 8 LTP, 75/25-BD/ST a t 41° F. Dresinate 214 Nitr C F 14 hr. a t 122" F. 76/30-BD/ST, Dresinate 731/
2
6.00-16
Finala Mileage 17,800
2
8.00-15
24,617
100
None
99
Xone
2
2
8.00-15
16,000
100
Mnd
7.2
100
Mod.
19 7
2
8.00-15
16,000
100
Mod.
12 4
103
91.
4 4
100 88
None Sone None
1.4 2.1 4 6
No. of Tires
4
Size
8.00-16
20,754
Wear Rating 100 105
Cracking Sone None
89
Cut Growth, Inches 1
1
0
40 40 40
6.70-15 6.70-15 6.70-15
17,000 17,000 17,000
100
99 101
h'one None Sone
...
HAP
2
8.00-15
16,000
100 91
Sone None
0.5 1.0
HAF
2
8.00-15
16,000
100 101
Kone None
0.6 1.6
HAF
4
6.70-15
16,000
100
0.8
118
2.0
. . ...
NaOR R . - .-.-
Final mileage records mileage used for rating tread wear based on nonskid depth, and does not indicate worn-out mileage of tire. b Tests run on Firestone test fleet.
a
TABLE XII. Test
KO.
LABORATORY PHYSICAL Min./ 280° F. 80 80 60 60 60 60
%!I?
Lb./&. Inch 750 850 1650 1650 1600 1825
Polymer OGR-S-AC X B659 2 0 x599 X 851-2-3 3 OX611 X D332-8 4 OD332-8 60 1725 XB1050-2-3 60 1425 Band X6110 60 1850 6 D346-5lC 60 1200 D352-8C 60 1475 7 OX611 60 1800 X D352-8 60 1975 8 OX611 60 1975 X D352-8 60 2375 9 OX611 60 X X679 60 3000 Aged 2 days a t 212O F. in oven. 6 Aged 5 hours at 260' F. in air bomb. C Whole treads. 1
PROPERTIES O F
Tensile Lb./Sq: Inch 3300 3675 3850
Elongation, % 700 660 620
3325 3275 3200 3325 3375 3750 2600 2950 3575 3250 3700 3475
540 520 460 510 570 530 550 510 540 450 490 360
4iic
460
NITRAZOLE
AND C O N T R O L TRE.4D S T O C K S
temperatures developed in factory affectedthe ultimate tread wear. Therefore, tests 7 and 8 were run to compare laboratory pressed treads with factory tubed treads. I n this case, the factory treads gave the best results. The variability of results obtained in road t,este to this point in the program, as well as the high tubing temperature and other indications of poor processability which were encountered, suggested instability of .. the polymer during fact,ory .. .. .. .. .. processing. Therefore, a program was set' up to s h d y the st'abilizing effect of various compounds on X679 (fact'ory batch of 122" F. Nitrazole C F polymer) a t high temperatures in a laboratory Banbury mixer. The stabilizing agent a t the level of 0.5 part, per hundred of rubber was introduced on a cool mill and the stabilized polymer u-as t,hen
.4ged Tensilea, Oper. Lb./Sq. Temp., Inch F. 2350 287 2700 261 2950 276 2850 ' 286 3000 268 3125 264 2700 304 2975 302 3250 267 2975 315 2900 280 3050 255 2875 249 3350 259 2800 247
.. ..
Q
Internal Friction, Kps. a t 100°C. 6 3 5 6 7 0 6 7 7.6 7.8 7.1 7.6 7.0 7.9 6.6 6.3 6.1 6.2 5.6
Cut Growth, 0.01 Inch/ Hourb 843 900 250 269 314 590 486 529 204 23 1 160 272 361 262 516
ing GR-S-Be and Ktrazole C F polymer. The other eight tests listed in Table X I compare Sitrazole CF polymer to X611 in HAF black stocks. Wear ratings range from 118 for X679 (factory batch of Nitrazole CF polymer) in test 9 to the 88 and 89 obtained in test 5 . TABLE XIII. EVALUATION OF STABILIZERS FOR X679 (122" F. ~YITRAZOLE C F POLYMER) The same stocks when run in 6.70-15 t,ires in test 6 gave (High temperature Banbury massing) Original 9 A h . a t 350' F. 6 Min. a t 350" F. wear ratings of 99 and 101, Original Test Material ML/4/212 Gel, % ML/4/212 Gel, % ML/4/212 Gel, % ML/4:212 Gel, % respectively. Treads for both Santol,ar 41 0.5 29 0.9 41 1.1 28.5 1.5 0.5 31.5 of these tests were tubed in the Antioxidant Hydroquinone 2246 41 0.8 46 1.6 34 17.5 44 1.3 35.6 22.0 42 1.3 38.5 27.0 factory from the eame stocks Control, blank 43 1.1 56 33.0 42 0.9 49 35.9 42.5 1.5 42.5 35.5 39 0.9 37 45.5 and it is felt that the test re45 1.1 54 37.1 41.5 1.1 55.5 42.0 Mercaptobenzothiazole 40.5 1 , ~ 42 43.7 sults represent the variation 42 4.3 34 47.7 2-Methyl-5-butylphenol possible under different test + acetaldehyde 43 1.3 51.5 42.0 40.5 1.1 37.5 45.2 conditions, and that the high 6
INDUSTRIAL AND ENGINEERING CHEMISTRY
June 1953
1321
A
B
C
D
E
F
Figure 2. X-Ray Diffraction Patterns of Nitrazole CF-Initiated Copolymers with Cold Rubber and GR-S Controls, Showing Degree of Order 1AR11. Nitrazole CF, 4 1 O F. Elongated 500% a t -55' C. Strong order B1051-54-58. Nitrazole CF, 8 6 O F. Elongated 480% at -55' C. Medium order C. B1050-52-53. Nitrazole CF, 122O F. Short cycle. Elongated 430% a t -55" C. No order D. D332-338. Nitrazole CF, 122O F. Long cycle. Elongated 440% a t - 5 5 O C. No order E. X599. Low temperature copolymer 80" F. Elongation 800% a t -55' C. Slightly ordered F. Regular GR-S C36l,12Z0 F. Elonwted 490% a t -55' C. Slightly ordered A. B.
-
massed in a 350" F. Banbury for 6 and 9 minutes. The effectiveness of the various materials was measured by Mooney plasticity and gel determinations on the various samples before and after the Banbury treatment. The most effective stabilizer for X679 was found to be Santovar 0 (2,5-di-tert-butylhydroquinone) (Table XIII). The results indicated that an increase in gel content, but not Mooney plasticity, will occur in this polymer during high temperature processing. The sodium dimethyldithiocarbamate and sulfur stopping agent and phenyl-2-naphthylamine (PBNA) antioxidant have been shown t o protect the polymer during processing a t the synthetic plant, but they are
apparently inadequate at the +300 F. temperatures encountered in the tire factory. Santovar 0 when added to the dry rubber before compounding (0.5 part per hfindred of rubber) increased stability. (Subsequent studies have shown that the requirements for the addition of Santovar 0 t o Nitrazole CF polymer latex were higher because apparently not all of the material added was available for stabilizing.) It was concluded that the addition of 0.5 part of Santovar 0 to the Banbury batch immediately after charging the polymer was a suitable method of application for polymer already prepared. This technique was utilized in factory runs and resulted O
OF FLEET TESTRESULTS ON NITRAZOLE C F POLYMERS IN TIRES TABLE XIV. SUMMARY
Polymers made a t reduced temperature. 0 and X = control and experimental halves of treads) Carbon No. of Final Wear Cut Growth, Feature Black Tires Sire Mileage Rating Cracking Inches LTP, 75/25-BD/ST a t 41° F. HAF 2 8.00-15 11,000 100 None 2.2 Dresinate 214 Nitr. C F a t 41' F 70/30-BD/ST, 75 None 0.4 KORR boa 80 hr. &ole Nitr. CF, ! 4 l%. at 122O F., 70/30-BD/ HAF 2 8.00-15 11,000 100 None 2.6 S T Dresinate 73 l/NaORR 83 None 0.4 HAF 2 8.00-15 8,000 and 100 None 1.0 12,000 104 and None 1.2 Nitr CF a t 41° F 70/30-BD/ST, Diesinate 731/NaORR, 40-hr. cycle 93 HAF 2 8.00-15 8,000 and 100 None 0.3 12,000 77-89 None 0.2 Nitr. CF a t 41° F. 70/30 BD/ST KORR, 26-hr. cycle
(Tire tests run on Firestone fleet. Test No. 10
Polymer No. OX611 XB1084-103
11
0 D352-8
12
X B1084-103 OX611 X B1132-4
13
OX611 X B1131
1322
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE XFT. LABORATORY PHYSICAL PROPERTIE$ O F LOW TEVPERATURE h’ITRAZOLE CONTROL TREADSTOCKS Tensile Lb./S&. Lb./Sq.’ Polymer Inch Inch OX611 60 2050 4025 X B1084-103 60 1800 3750 60 1325 3100 11 OD352-8 XB1084-103 60 1650 3600 60 1975 3600 12 OX611 X B1132-4 60 2825 3500 60 1975 3600 13 OX611 X B1131 60 2325 3525 a Aged 2 days at 212’ F. in oven. b Aged 5 hours a t 260” F. in air bomb.
Test No. 10
Min./ 280” F.
Elongation, % 540 600 580 570 510 360 510 420
Aged Tensilea Lb./Sq.’ Inch 3300 3250 3075 3075 3375 3300 3375 3350
in lower tubing temperatures and smoother treads. Some of the variation in wear results may be related to accelerator changes dictated by the tubing temperatures. For example, in test 9 (Table XI), Santovar 0 (0.5 part) was added during factory mixing and normal tread tubing temperatures were realized. This permitted a somewhat higher accelerator level than would otherwise have been possible. FLEET TESTS OF NITRAZOLE C F POLYMERS MADE AT REDUCED TEMPERATURES
Table XIV lists the results of tire tread tests on Nitrazole C F polymers made a t 86” and 41” F. The wear ratings obtained show these particular Nitrazole CF polymers made at reduced temperatures to be inferior in abrasion resistance t o both X611 and 122’ F. Nitrazole C F polymer. Physical properties of the tread stocks are presented in Table XV. ACKNOWLEDGMENT
The authors wish to thank the following collaborators for their assistance on certain sections of this report: R. L. Bebb, suggestions and encouragement; J. W. Ballard, x-ray diffraction
Oper. Temp., F. 262 282 304 288 273 238 273 260
Internal Friction, Kps. a t l o O D C.
AND
Vol. 45, No. 6 studies; and J. L. Binder, infrared spectra.
(:ut
Growth, 0.01 Inch/
6 6
6.9 7.6 7.1 7.1 5.9 7.1 6.4
Hr. b 144 336 238 544 162 510 162 900
LITERATURE CITED
(1) Burk, R. E. (to E. I. du Pont de Nemours & Co.), U. S. Patent 2,500,023 (March 7 , 1950). (2) Bysow, B., Russian Patent 1103 (July20, 1927); Ger. Patent 521,903 (March 12, 1931). (3) Fryling, C. S. (to B. F. Goodrich Co.), U. S.Patent 2,313.233 (March 9. 1943). 14) Garvev. B. S. (to’ B. F. ’ Goo&ich Co.), Ibid., 2 , 276,963 (May 29, 1945).
Hickinbottom, W. J., ”Reactions of Organic Compounds,” 2nd ed., pp. 383-5, Xew York, Longmans, Green & Co., 1948. Hunt, M. (to E. I. du Pont de Nemours & Co.), U. S. Patent 2,471,959 (May 31, 1949). Johnson, B. L., and Wolfangel, R. D.. IND.ENQ.CHEY.,41, 1580 (1949).
Marks, B. &I. (to E. I. du Pont de Nemours & Co.), U. S. Patent 2,516,064 (July 18, 1950). Pratt, L. S., “Chemistry and Physics of Organic Pigments,” Xew York, John Wiley & Sons, 1947. Reynolds, W. B., and Cotten, E. W., IND. ENG.CHEM.,42, 1905 (1950).
Robertson, J. A. (to E. I. du Pont de Semours & Co.), U. S. Patent 2,520,338 (Aug. 29, 1950). Ibid., 2,520,339 (Aug. 29, 1950).
Saunders, K. H., “Aromatlc Diazo Compounds and Their Technical Applications,” London, Edward Arnold, 1949. Semon, W. L., and Fryling, C. F. (to B. F. Goodrich Co.), U. S.Patent 2,376,014 (May 15, 1945). Walker, H. W. (to E. I. du Pont de Nemours & Co.), Ibid., 2,382,684 (Aug. 14, 1945).
RECEIVED for review Sovember 4, 1952. ACCEPTEDFebruary 9, 1953. Presented before the Division of Rubber Chemistry, A ~ Z R I C ACHEMICAL N Buffalo, W. Y., October 1952. Work performed as part of research SOCIETY, project sponsored by Reconstruction Finance Corp., Synthetic Rubber Division. in connection with the government synthetic rubber program.
Tensile Properties of Films from Low Temperature GR-S Latex R. W. BROWN, W. E. MESSER, AND L. H. HOWLAND Naugatuck Chemical Division, United States Rubber Co., Naugatuck, Conn.
T
HE tensile properties of evaporated films from synthetic
rubber latex are of interest from both theoretical and practical considerations. From the theoretical point of view., film tensiles give a measure of the inherent properties of polymers which have not been subjected to processes of flocculation and mastication. Practically, film tensiles may be used to predict the approximate tensile properties of latex-derived polymer in some technical applications, although results will not be directly comparable because of the different conditions employed. Natural rubber films have been the object of many investigations and their excellent tensile properties are well known (3). It is also well established that GR-S latex containing predominant amounts of butadiene and polymerized at high temperatures (about 40’ C.) gives films with tensile strengths on the order of 10% of those from natural rubber latex (5, 8, 9). This value can be increased to about one half that of natural rubber by increasing the amount
of styrene in the copolymer to around 50%, but only with the sacrifice of much of the rubberlike quality of the polymer, particularly a t subfreezing temperatures (8, 9). With the development of low temperature GR-S polymerization, new latices became available, and early work on low-solids latex which had been concentrated by creaming indicated that a very marked improvement in film tensiles was achieved by lowering the temperature of polymerization (6). Film tensiles of 2500 to 3300 pounds per square inch were obtained on three latices prepared a t 5’ C., and values in excess of 4000 pounds per square inch were obtained from one latex prepared a t - 18” C. These results were six to ten times as great as are normally obtained from latex of the same monomer ratio polymerized a t high temperatures. Following this work, low temperature (10’ C.) recipes for high-solids latices were developed and put into commercial production ( 3 , 6, 7 ) . Although these latices gave much improved
